A field experiment was carried out in the years 1996–1998 at the Experimental Farm in Zawady, on the very good rye complex soil of quality class IVa. The experiment was established in a random blocks design in three replications. Varied partcipation of faba bean (0, 25, 50,
75, 100%) and spring wheat (100, 75, 50, 25, 0%) in the mixtures was the experimental factor. The aim of the study was to determine the yielding and changes in the nutrient content in the biomass of the mixtures of faba bean and spring wheat intended to be entirely used as feedstuff, respective to the participation of components. The following characteristics were studied: the yield of dry matter, the yield of total protein, the content of crude protein, crude fat, crude fibre, crude ash and niterogen free extract. The dry matter and total protein yield as well as the content of nutrients in the biomass varied according to the participation of components in the mixture. However, there was no significant influence of the participation of components on the weeding of the sown area. The highest dry matter yield was obtained in the case of the mixture with 50-percent faba bean and spring wheat whereas the total protein yield was highest in the case of the treatment with 75 and 100-percent participation of faba bean. Increased participation of faba bean was followed by an increase in the content of total protein, crude fibre and crude ash and reduction in the content of crude fat and nitrogen free extract compounds.